Aphids & How to Rid Them From My Bonsai

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Even the smallest bonsai is big enough to host a thriving colony of aphids. Your tiny treasure is fair game for at least one of roughly 200 aphid species that threaten garden and houseplants. Blessed with petite dimensions, long-legged, pear-bodied aphids crowd onto leaves and stems to feed and reproduce. They reward your bonsai’s hospitality with physical and cosmetic damage. Quick action remedies both.

How Aphids Attack

Aphids attach to your bonsai with sharp, hollow mouth tubes. Pressure within the bonsai's fluid-conducting phloem cells automatically forces sap into the tubes. This system allows the nitrogen-craving aphids to consume far more sap than they can possibly digest. After metabolizing the nitrogen, they excrete the sugar-laden leftovers as sticky waste droplets, called honeydew. Ants and sooty mold spores often arrive to live off this goo.

Physical Damage

Sooty mold spores germinate into blackish, greasy deposits, blemishing the bonsai without actually penetrating it. Far more dangerous is the potential physical toll from an aphid attack. Infested foliage may wrinkle, curl, distort, wilt or fade to yellow and brown from loss of chlorophyll. A flowering bonsai may drop its buds. Branch-feeding aphids often shelter inside abnormal gall formations. Some plants have toxic reactions to substances in aphid saliva. These pests, in other words, have nothing good in mind for your bonsai.

Tender Loving Aphid Removal

With some adjustments, the traditional aphid removal technique for larger plants also succeeds on bonsai. Support each branch or stem of an outdoor bonsai, or an indoor one placed in your sink, with one hand. With the other, dislodge the insects with a stream of water from a hose or faucet sprayer attachment. Rinsing with a solution of mild dish soap and water washes off honeydew and sooty mold.

Biological Bullies

Several insects prey on aphids. To take advantage of this biological control, release commercially available convergent lady beetles (Hippodamia convergens) on your outdoor bonsai. The University of California Statewide Integrated Pest Management Program recommends refrigerating the beetles before a nighttime release. After misting the plant and the beetles, set the beetles on the base of the bonsai or its lowest branch crotches. They'll climb as they hunt for the aphids. Depending on the severity of the infestation, you may need a second release in a week.

Suffocation By Soap

Ready-to-use insecticidal soap suffocates aphids it reaches without leaving toxic residue. Before treating your bonsai, swab a small area of it with the soap and wait 48 hours. If there's no reaction, the soap is safe to use. Water your plant well and spray it when the temperature ranges from 40 to 90 degrees Fahrenheit. Coat it thoroughly with soap, giving extra attention to the leaves' undersides. Follow-up treatments at the label's recommended intervals, usually every seven to 10 days, eliminate the aphids you miss, as well as their offspring.

About the Author

Passionate for travel and the well-written word, Judy Wolfe is a professional writer with a Bachelor of Arts in English literature from Cal Poly Pomona and a certificate in advanced floral design. Her thousands of published articles cover topics from travel and gardening to pet care and technology.